Response of Ar v O2 on a TCD

[mcdonar2000]

In theory, Ar should give a larger response (per unit vol) than oxygen with He carrier gas (due to having higher TC differential from He than oxygen), but practically, I've found that this may not be the case. Can anyone explain please?

Thanks...

[JI2002]

A few factors affect the sensitivity of TCD. In addition to thermal conductivity difference between the carrier gas and the analyte, molecular weight of the analyte is another one. Oxygen has a smaller molecular weight which gives it better response. Also, the sensitivity of TCD is very sensitive to the temp of the detector. The sensitivity goes down as TCD temp increases. Argon and oxygen could behave differently in different TCD temp.

[mcdonar2000]

Thanks for the reply, it explains a few things. Much appreciated.

[CIL-BAHA]

The word ..may... doesn't tell us much, however, I was told TCD's MAJOR PROBLEM was keeping the dual flows of detector reference gas constant.